PBR painting directly
Yes,Thise is possible using a new branch under developing right now (Not officially).

All you have to do is to create images in the image editor and use them in your nodetree,and you can paint in the viewport of in the image editor.

You can see PBR painting at the end of this video

And you can download the branch from here.

Edit for the question in the comments:

Yes you can in the viewport painting,just check cavity mask and edit the curve to get what you need,
But I love doing it procedurally using nodes and pointiness feature.